Propionic acid

Propanoic acid

Names
Preferred IUPAC name Propanoic acid
Other names Propionic acid Ethanecarboxylic acid
Identifiers
CAS Number	79-09-4 Y
3D model (Jmol)	Interactive image Interactive image
ChEBI	CHEBI:30768 Y
ChEMBL	ChEMBL14021 Y
ChemSpider	1005 Y
DrugBank	DB03766 Y
ECHA InfoCard	100.001.070
EC Number	201-176-3
E number	E280 (preservatives)
IUPHAR/BPS	1062
PubChem	1032
RTECS number	UE5950000
InChI InChI=1S/C3H6O2/c1-2-3(4)5/h2H2,1H3,(H,4,5) Y Key: XBDQKXXYIPTUBI-UHFFFAOYSA-N Y
SMILES CCC(=O)O CCC(=O)O
Properties
Chemical formula	C3H6O2
Molar mass	74.08 g·mol−1
Appearance	Colorless, oily liquid
Odor	Pungent, rancid, unpleasant
Density	0.98797 g/cm3
Melting point	−20.5 °C (−4.9 °F; 252.7 K)
Boiling point	141.15 °C (286.07 °F; 414.30 K)
Sublimation conditions	Sublimes at −48 °C ΔsublHo = 74 kJ/mol
Solubility in water	8.19 g/g (−28.3 °C) 34.97 g/g (−23.9 °C) Miscible (≥ −19.3 °C)
Solubility	Miscible in EtOH, ether, CHCl3
log P	0.33
Vapor pressure	0.32 kPa (20 °C) 0.47 kPa (25 °C) 9.62 kPa (100 °C)
Henry's law constant (kH)	4.45·10−4 L·atm/mol
Acidity (pKa)	4.88
Magnetic susceptibility (χ)	-43.50·10−6 cm3/mol
Thermal conductivity	1.44·105 W/m·K
Refractive index (nD)	1.3843
Viscosity	1.175 cP (15 °C) 1.02 cP (25 °C) 0.668 cP (60 °C) 0.495 cP (90 °C)
Structure
Crystal structure	Monoclinic (−95 °C)
Space group	P21/c
Lattice constant	a = 4.04 Å, b = 9.06 Å, c = 11 Å α = 90°, β = 91.25°, γ = 90°
Dipole moment	0.63 D (22 °C)
Thermochemistry
Specific heat capacity (C)	152.8 J/mol·K
Std molar entropy (So298)	191 J/mol·K
Std enthalpy of formation (ΔfHo298)	−510.8 kJ/mol
Std enthalpy of combustion (ΔcHo298)	1527.3 kJ/mol
Hazards
Main hazards	Corrosive
GHS pictograms
GHS signal word	Danger
GHS hazard statements	H314
GHS precautionary statements	P280, P305+351+338, P310
EU classification (DSD)	C
R-phrases	R10, R34
S-phrases	(S1/2), S23, S36, S45
NFPA 704	2 3 0
Flash point	54 °C (129 °F; 327 K)
Autoignition temperature	512 °C (954 °F; 785 K)
Lethal dose or concentration (LD, LC):
LD50 (median dose)	1370 mg/kg (mouse, oral)
US health exposure limits (NIOSH):
PEL (Permissible)	none
REL (Recommended)	TWA 10 ppm (30 mg/m3) ST 15 ppm (45 mg/m3)
IDLH (Immediate danger)	N.D.
Related compounds
Other anions	Propanoate
Related Carboxylic acids	Acetic acid Lactic acid 3-hydroxypropionic acid Tartronic acid Acrylic acid Butyric acid
Related compounds	1-Propanol Propionaldehyde Sodium propionate Propionic anhydride
Except where otherwise noted, data are given for materials in their standard state (at 25 °C [77 °F], 100 kPa).
Y  (what is YN ?)
Infobox references

Propionic acid (from the Greek words protos, meaning "first", and pion, meaning "fat"; also known as propanoic acid) is a naturally occurring carboxylic acid with chemical formula CH₃CH₂COOH. It is a clear liquid with a pungent and unpleasant smell somewhat resembling body odor. The anion CH₃CH₂COO⁻ as well as the salts and esters of propionic acid are known as propionates (or propanoates).

Propionic acid was first described in 1844 by Johann Gottlieb, who found it among the degradation products of sugar. Over the next few years, other chemists produced propionic acid in various other ways, none of them realizing they were producing the same substance. In 1847, the French chemist Jean-Baptiste Dumas established all the acids to be the same compound, which he called propionic acid, from the Greek words πρῶτος (prōtos), meaning first, and πίων (piōn), meaning fat, because it is the smallest H(CH₂)_nCOOH acid that exhibits the properties of the other fatty acids, such as producing an oily layer when salted out of water and having a soapy potassium salt.

Propionic acid has physical properties intermediate between those of the smaller carboxylic acids, formic and acetic acids, and the larger fatty acids. It is miscible with water, but can be removed from water by adding salt. As with acetic and formic acids, it consists of hydrogen bonded pairs of molecules as both the liquid and the vapor.